exchanging Shimano cassettes ?
08-29-20, 03:38 PM
#1
Newbie
Thread Starter
Join Date: Aug 2020
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Likes: 0
Liked 2 Times
in
2 Posts
exchanging Shimano cassettes ?
Greetings. Thanks in advance for any input.
I have a GRX 1x11 drivetrain. I would like to replace the current CS-M7000-11 (11-42T) cassette with a CS-HG800-11 (11-34T) cassette. Am I correct in thinking this is a straight-up 1 for 1 exchange; no shims, or other alterations needed and the new cassette is compatible with the rest of the drivetrain? The RD is a RX812 and the crankset is an FC-RX600.
I have never removed / installed a cassette before. The videos make it look pretty easy and I am reasonably proficient - but if anyone wants to offer any tips, tricks, or things I should be aware of before starting, I would gratefully read them!
Backstory, if you are interested: This is for a new gravel bike (Giant Revolt Advanced 1). Coming from MTBs with 1x systems, I thought this was the way to go with the gravel bike. I will admit now that I see the point of the 2x systems. I did not mind the gear jumps on the MTB, but it is noticeable and slightly annoying on the gravel bike. However, I exclusively ride this bike in the flat coastal plain (can't find a real hill if you tried), so I think a very workable solution is to switch the cassette and stay with the 1x system that I otherwise love and would prefer to stick with.
I have a GRX 1x11 drivetrain. I would like to replace the current CS-M7000-11 (11-42T) cassette with a CS-HG800-11 (11-34T) cassette. Am I correct in thinking this is a straight-up 1 for 1 exchange; no shims, or other alterations needed and the new cassette is compatible with the rest of the drivetrain? The RD is a RX812 and the crankset is an FC-RX600.
I have never removed / installed a cassette before. The videos make it look pretty easy and I am reasonably proficient - but if anyone wants to offer any tips, tricks, or things I should be aware of before starting, I would gratefully read them!
Backstory, if you are interested: This is for a new gravel bike (Giant Revolt Advanced 1). Coming from MTBs with 1x systems, I thought this was the way to go with the gravel bike. I will admit now that I see the point of the 2x systems. I did not mind the gear jumps on the MTB, but it is noticeable and slightly annoying on the gravel bike. However, I exclusively ride this bike in the flat coastal plain (can't find a real hill if you tried), so I think a very workable solution is to switch the cassette and stay with the 1x system that I otherwise love and would prefer to stick with.
08-29-20, 04:01 PM
#2
Senior Member
Join Date: May 2003
Location: Mountain Brook. AL
Posts: 4,002
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 303 Post(s)
Likes: 0
Liked 136 Times
in
104 Posts
The HG 800 and HG 700 (nearly the same Ultegra vs 105) are oddities in that they are 11 spd cassettes designed
to fit on 8-9-10 speed freehubs. They are shipped with the spacer needed if used on an 11spd freehub. Should be
in the box with the cassette. Put the spacer on first, then the rest of the cassette. As per Shelby, the lockring when
tightened has 'click stops', it has been a while and I always use a torque wrench, but you need to tighten it up 5-6 clicks
and then maybe one more click, it takes a bit of effort.
Well Shelby's post is gone, but he also mentioned the probable need to shorten the chain as well, by 3-4". If the
chain has more than 2000 or so miles on it, it may be too worn for the new cassette. Check chain for wear also.
to fit on 8-9-10 speed freehubs. They are shipped with the spacer needed if used on an 11spd freehub. Should be
in the box with the cassette. Put the spacer on first, then the rest of the cassette. As per Shelby, the lockring when
tightened has 'click stops', it has been a while and I always use a torque wrench, but you need to tighten it up 5-6 clicks
and then maybe one more click, it takes a bit of effort.
Well Shelby's post is gone, but he also mentioned the probable need to shorten the chain as well, by 3-4". If the
chain has more than 2000 or so miles on it, it may be too worn for the new cassette. Check chain for wear also.
Last edited by sch; 08-29-20 at 04:10 PM.
Likes For sch:
08-29-20, 04:58 PM
#3
Senior Member
Join Date: Sep 2010
Location: Roswell, GA
Posts: 8,319
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1438 Post(s)
Liked 1,092 Times
in
723 Posts
It is not strictly necessary to shorten the chain; presumably the system shifted the 34T and smaller cogs of the original cassette just fine. But a shorter chain my give a little faster shifting; the difference may or may not be noticeable. I like to keep chains and cassettes together as a set; sch's suggestion of a new chain may have merit.
08-29-20, 06:32 PM
#4
Really Old Senior Member
I wouldn't shorten the chain just yet. Nor do you need to.
One can make a case that you spread the "work" over more links. A link spends X time working and Y time idling. More links means a greater % idle time.
I don't know if you're done on your quest, but what if you decide you really want a 36T cog. You may have already decided that maybe you want to go smaller?
Maybe split the diff between what you have and what you can shorten?
Just no need to rush into anything yet. You are "safe" cutting nothing.
One can make a case that you spread the "work" over more links. A link spends X time working and Y time idling. More links means a greater % idle time.
I don't know if you're done on your quest, but what if you decide you really want a 36T cog. You may have already decided that maybe you want to go smaller?
Maybe split the diff between what you have and what you can shorten?
Just no need to rush into anything yet. You are "safe" cutting nothing.
08-29-20, 06:35 PM
#5
Expired Member
Join Date: Jun 2007
Location: TN
Posts: 11,543
Mentioned: 37 Post(s)
Tagged: 0 Thread(s)
Quoted: 3673 Post(s)
Liked 5,430 Times
in
2,759 Posts
Sorry for any confusion. I deleted my post because I'd forgotten about the 34T cassette/spacer issue. Stupid on my part, especially since I have one.... 
42T to 34T is a pretty big reduction. If your chain is flopping around you need to make it shorter.
42T to 34T is a pretty big reduction. If your chain is flopping around you need to make it shorter.
08-29-20, 07:01 PM
#6
Senior Member
Join Date: Mar 2010
Posts: 1,659
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1248 Post(s)
Liked 1,323 Times
in
674 Posts
The GRX has a clutch and since it is within the range of the original cassette no problem with length and no floppy. Clamp it on and all good.
08-29-20, 07:04 PM
#7
Expired Member
Join Date: Jun 2007
Location: TN
Posts: 11,543
Mentioned: 37 Post(s)
Tagged: 0 Thread(s)
Quoted: 3673 Post(s)
Liked 5,430 Times
in
2,759 Posts
Good to know the clutch can take up that much extra chain
08-29-20, 07:22 PM
#8
Newbie
Thread Starter
Join Date: Aug 2020
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Likes: 0
Liked 2 Times
in
2 Posts
Thanks all for the quick and helpful replies!
No, I am perhaps not done with my search, so I will leave chain length as if for now. But if it seems floppy, it is easy enough to shorten later.
SCH mentioned using a torque wrench. I've got one - anybody know what the recommended torque is?
No, I am perhaps not done with my search, so I will leave chain length as if for now. But if it seems floppy, it is easy enough to shorten later.
SCH mentioned using a torque wrench. I've got one - anybody know what the recommended torque is?
Last edited by SwampGrinder; 08-29-20 at 07:24 PM. Reason: clarity
08-29-20, 07:52 PM
#9
Really Old Senior Member
08-30-20, 02:11 PM
#10
Newbie
Thread Starter
Join Date: Aug 2020
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Likes: 0
Liked 2 Times
in
2 Posts
Good to know. Thanks! I have not yet purchased the cassette - wanted ask folks here whether if was compatible before ordering (since it is not available anywhere local to me). But I am now keen to get it and see how it changes the ride.
08-30-20, 04:54 PM
#11
Full Member
Caveat: maybe I've been doing it wrong.
With road/gravel wheels I use a spacer with the Shimano 11-speed MTB cassettes (between freehub body and largest sprocket), but remove the spacer when installing a road cassette, like the 11-34.
With road/gravel wheels I use a spacer with the Shimano 11-speed MTB cassettes (between freehub body and largest sprocket), but remove the spacer when installing a road cassette, like the 11-34.
